The present invention relates to a two-piece solid golf ball. More particularly, it relates to a two-piece solid golf ball having long flight distance when hit by a middle iron club to a driver, large spin amount when hit by a short iron club and the like and excellent controllability, while maintaining good shot feel as good as thread wound golf ball.
Golf balls having various structures are commercially selling. There are generally solid golf balls represented by two-piece golf ball and thread wound golf balls for round games. The two-piece solid golf balls have excellent flight performance and durability as compared with the thread wound golf balls. Therefore the two-piece solid golf balls occupy the greater part of the golf ball market. However, the two-piece solid golf ball is inferior to the thread wound golf ball in shot feel and controllability at approach shot.
There has been many suggestions in order to further improve performances of the two-piece solid golf ball. For example, in Japanese Patent Kokai publication Nos. 220889/1988, 98949/1994, 194732/1995 and the like, a two-piece solid golf ball, of which performances, such as flight distance (rebound characteristics), durability, shot feel and controllability are improved by mainly adjusting hardness or hardness distribution of the core to a proper range, is suggested. In Japanese Patent Kokai publication No. 127823/1998, a two-piece solid golf ball, of which performances are improved by adjusting thickness and hardness of the cover, and hardness distribution of the golf ball to proper ranges, is suggested.
In Japanese Patent Kokai publication No. 220889/1988, a two-piece solid golf ball having a hardness distribution in JIS-C hardness such that a hardness at the distance of less than 10 mm from the center point of the core is within the range of 60 to 79 and a hardness at the distance of more than 10 mm from the center point is within the range of 80 to 90; a thickness of the cover of 1.5 to 2.0 mm; and a deformation amount of the golf ball of 1.9 to 2.4 mm when applying from an initial load of 10 kgf to a final load of 130 kgf; is disclosed. However, in the golf ball, it is problem that the deformation amount of the golf ball is small, that is, the golf ball is hard, and its shot feel is poor.
In Japanese Patent Kokai publication No. 98949/1994, a two-piece solid golf ball having a hardness distribution of the core such that a hardness of the core is higher in order at the center point of the core, at the distance of 5 to 10 mm from the center point, at the distance of 15 mm from the center point and at the surface of the core is disclosed. However, in the golf ball, the cover is formed from relatively hard material, and its flight distance is long, but it is problem that its spin amount when hit by a short iron club and the like is small, which degrades its controllability.
In Japanese Patent Kokai publication No. 194732/1995, a two-piece solid golf ball having a center hardness in JIS-C hardness of the core of 40 to 57, a surface hardness in JIS-C hardness of the core of 70 to 95, and a difference between the surface hardness and center hardness of 20 to 40 is disclosed. However, also in the golf ball, the cover is formed from relatively hard material, and it is problem that its spin amount when hit by a short iron club and the like is small, which degrades its controllability.
In Japanese Patent Kokai publication No. 127823/1998, a two-piece solid golf ball having a thickness of the cover of 1.0 to 2.1 mm, which is thin; a JIS-C hardness of the cover of 75 to 95; and a hardness distribution such that a difference between the cover hardness and a center hardness in JIS-C hardness of the core is not more than 10, which is small; is disclosed. However, in the golf ball, the cover is formed from only ionomer resin, and it is problem that its rebound characteristics is poor, and its flight distance when hit by a driver is short.
It is required to provide a two-piece golf ball having excellent flight performance, good shot feel and controllability by solving the problems. Recently, multi-piece solid golf balls having excellent flight performance, good shot feel and controllability, as compared with a conventional two-piece solid golf ball, are developed. Therefore it is required to further improve the flight performance, shot feel and controllability also in the two-piece golf ball.
A main object of the present invention is to provide a two-piece solid golf ball having long flight distance when hit by a middle iron club to a driver, large spin amount when hit by a short iron club and the like and excellent controllability, while maintaining good shot feel as good as thread wound golf ball.
According to the present invention, the object described above has been accomplished by employing a blend of ionomer resin and high rebound characteristics thermoplastic elastomer in the cover, and adjusting the hardness distribution of the core and golf ball to specified ranges, thereby providing a two-piece solid golf ball having long flight distance when hit by a middle iron club to a driver, large spin amount when hit by a short iron club and the like and excellent controllability, while maintaining good shot feel as good as thread wound golf ball.